It happened at the Deli Express on Knickerbocker Avenue in Bushwick on Sunday at 7:30 a.m.
The robbery was captured on surveillance video.
The video shows the suspect entering the location, displaying a black firearm, demanding money, and then running away with the money.
The suspect is described as a black male, wearing a baseball cap, gray hoodie, and blue jeans.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477).
You can also submit your tips by logging onto Crimestoppers' website at nypdcrimestoppers.com or by texting your tips to CRIMES (274637), and then entering TIP577.
All calls are strictly confidential.